A thread cutting device, in which an axially displaceable drive mechanism catches the needle thread and the shuttle thread in one of its directions of movement and pulls them out and feeds them to the cutting blade in its other direction of movement, has become known from a realized sewing machine design. To control the releasing mechanism for the thread tension, a cam actuating the release mechanism is fastened on the drive mechanism. Even though this measure ensures a very simple drive of the tensioning mechanism, it causes opening of the thread tensioning mechanism during the movement of the drive mechanism in both directions of movement. This leads to difficulties in catching the loop under critical thread conditions and also to unequal thread ends after the cutting process.